Bits for lathe tools

ABSTRACT

An interchangeable cutting bit for a machine tool, the bit consisting of a flat hexagonal body having a surrounding peripheral face comprising six facets, the peripheral face being formed with three straight swarf grooves each of which spans two adjacent facets and is slanted so that one end thereof lies adjacent to one side of the bit and at a corner thereof and the other end lies adjacent to the other side of the bit and at another corner thereof, the grooves each having two cutting edges arranged on opposite sides thereof one being disposed on each of the facets, the edges lying closely adjacent to the groove over their whole length.

United States Patent [191 Swann Apr. 9,1974

[ BITS FOR LATHE TOOLS [7 5] Inventor: Michael S. Swann, Aylesbury,

England [73] Assignee: Hoy Carbides Limited, Aylesbury,

Buckinghamshire, England 22 Filed: Dec.6,1971 21 App1.No.:205 ,226

[52] US. Cl. 29/96, 29/101 1,246,360 8/1967 Germany 29/96 Primary Examiner-Andrew R. Juhasz Assistant Examiner-Leon Gilden Attorney, Agent, or Firm-Brady, OBoyle & Gates [5 7] ABSTRACT An interchangeable cutting bit for a machine tool, the

bit consisting of-a flat hexagonal body having a surrounding peripheral face comprising six facets, the peripheral face being formed with three straight swarf grooves each of which spans two adjacent facets and is slanted so that one end thereof lies adjacent to one side of the bit and at a corner thereof and the other end lies adjacent to the other side of the bit and at another corner thereof, the grooves each having two cutting edges arranged on opposite sides thereof one being disposed on each of the facets, the edges lying closely adjacent to the groove over their whole length.

3 Claims, 4 Drawing Figures BITS FOR LATHE TOOLS This invention is concerned with bits for lathe tools and more particularly with interchangeable bits, i.e., bits adapted to be detachably secured to a holder as distinct from bits adapted to be permanently secured, e.g., by brazing, to a holder.

According to the present invention, there is provided an interchangeable cutting bit for a machine tool, the cutting bit having two hexagonal sides and a peripheral face having six facets extending round the bit between the sides, the peripheral face being provided with three straight grooves, each of which spans two facets of the peripheral face and extends from near a corner of one side of the bit to near a corner of the. other side of the bit, each groove having two cutting edges on opposite sides thereof extending along the associated facets and each groove being disposed closely adjacent to its associated cutting edges along their whole length to receive and guide swarf therefrom.

Each groove is preferably of V-section. Preferably the base or root of each groove lies on a straight line.

A narrow land is preferably provided between each cutting edge and the groove associated therewith.

The following is a description, by way of example, of an embodiment of the invention, reference being made to the accompanying drawings, in which:

FIG. 1 isa side view of an interchangeable bit;

FIG. 2 is a face view of the bit;

FIG. 3 is a fragmentary section view on line A--A in FIG. 2, and

FIG..4 is a side view of the bit in position in a holder.

The bitis made of suitable hard material, e.g., by pressing and grinding from tungsten carbide. It is hexagonal with two flat parallel hexagonal sides and a peripheral face 11 comprising six facets. The edges of each side are defined by the overlapping portion of a pair of congruent, equilateral triangles, the midpoints of which are coincident, after one triangle has been rotated about its midpoint relative to the other through substantially 25 The hexagonal sides thereby have alternate obtuse and acute corners and the angle of the acute corners is about 85, which is particularly suitable for the operative points of the bit which occur at said acute comers. The angle of the corners at which the operative points occur may be varied but should preferably not exceed 90, or be less than 60.

Three V-section grooves 12 are provided in the peripheral face 11, each groove having a root or base 13 lying on a straight line and having side walls at 90 to each other. Each groove 12 spans two facets of the peripheral face and extends from near an acute corner of one side of the bit to near an acute corner of the other side of the bit, as can be seen in FIG. 2. Each groove has associated therewith two cutting edges 14 which extend along the sides of the peripheral face 11 from the acute comers from and to near which the groove extends to the obtuse corners between which the groove extends. Thereby three cutting edges are spaced around each side of the peripheral face 11 but a cutting face on one side of that face is never opposite one on the other side.

The grooves extend close to the cutting edges over the whole length of the edges, being separated therefrom only by narrow lands 15.

The corners provided by the junction of the hexagonal sides of the bit and the peripheral faces are, where there are not cutting edges, radiused at and adjacent the acute corners, these radii tapering out through half the distance to the nearest obtuse corner.

The bit is secured, e.g., by a screw through a hole 15 in the bit to a suitable holder 16 having ashallow V- shaped seat 17 for locating the bit. The holder has a side support 19 to which the bit is fastened. When one cutting edge becomes worn, the bit can be rotated or reversed and rotated to bring another cutting edge into operating position.

The bit and holder shown in the drawings are for use in tangential roller boxes. The groove associated with the cutting edge being used receives swarf therefrom. and guides it away with little or no risk of entanglement with the rollers although the swarf will normally be produced in long coils. The bit may [however be used in other lathe tools, for example, cantilever type tools.

It will be seen that with the groove arrangement illustrated it is possible to produce grooves serving six cutting edges by only three grinding operations.

In the drawing, each groove 12 is shown as going through the forward edge of the peripheral face of the bit near the operative point and the land does not continue round the nose radius (indicated by 18 in FlG. 2). However the land may if desired continue round the nose radiusacross the forward edge.

I claim:

1. An interchangeable chipstream cutting bit for a roller box machine tool, comprising two opposite hexagonal sides and a peripheral face extending round the bit between said opposite sides, said hexagonal sides and connecting peripheral face forming alternate obtuse angle and acute angle corners around the bit, said peripheral face having formed therein three straight chip grooves each of which is V-shaped in cross-section and each of which extends from an acute angle comer and a position near one of said sides of the bit and through an obtuse angle corner to the successive acute angle corner and to a position near the other of said sides of the bit, each of said grooves having on opposite sides thereof two cutting edges extending along the sides of the peripheral face from an acute angle corner to an obtuse angle corner, a narrow land formed between each cutting edge and its associated groove whereby each groove is disposed closely adjacent to each of its cutting edges along the whole length of each of its cutting edges and adapted to receive and guide swarf therefrom, and the base or root of each groove being rectilinear.

2. An interchangeable cutting bit as set forth in claim 1 in which the angle of said acute angle comers is about 3. An interchangeable cutting bit as set forth in claim 1 in which the angle of said acute angle comers is in the range of 60 to 

1. An interchangeable chipstream cutting bit for a roller box machine tool, comprising two opposite hexagonal sides and a peripheral face extending round the bit between said opposite sides, said hexagonal sides and connecting peripheral face forming alternate obtuse angle and acute angle corners around the bit, said peripheral face having formed therein three straight chip grooves each of which is V-shaped in cross-section and each of which extends from an acute angle corner and a position near one of said sides of the bit and through an obtuse angle corner to the successive acute angle corner and to a position near the other of said sides of the bit, each of said grooves having on opposite sides thereof two cutting edges extending along the sides of the peripheral face from an acute angle corner to an obtuse angle corner, a narrow land formed between each cutting edge and its associated groove whereby each groove is disposed closely adjacent to each of its cutting edges along the whole length of each of its cutting edges and adapted to receive and guide swarf therefrom, and the base or root of each groove being rectilinear.
 2. An interchangeable cutting bit as set forth in claim 1 in which the angle of said acute angle corners is about 85*.
 3. An interchangeable cutting bit as set forth in claim 1 in which the angle of said acute angle corners is in the range of 60* to 90*. 